The WavePoint T5 HO bulbs will work in any T5 HO fixture as long as you are using bulbs of the same wattage as those currently in your fixture. T5 bulbs come in two categories: NOs are either 9W, 14W, 21W or 28W; HOs are 24W, 39W or 54W. T5 lamps are 5/8" (.625") diameter.